1. Field
The following description relates to a switch control technology. The following description also relates to a switch control circuit, method, and a converter using the same capable of controlling a stable average current regardless of an input change, a peripheral parts change, a load change or a switch off-time.
2. Description of Related Art
A power supply is an apparatus that supplies a power to a load. A buck converter, one of the power supplies, corresponds to a step-down DC-DC converter. That is, such a converter outputs a voltage that is lower than an input voltage. The buck converter uses an inductor and two switches, for example, where the two switches are a transistor and a diode, controlling the inductor to repeatedly perform a process of storing an energy supply in the inductor and that of discharging the inductor to a load.
A linear regulator may be used instead of a buck converter to lower the voltage of a DC power supply. However, the use of a linear regulator presents an issue that the waste of energy that occurs as it operates is high because a linear regulator operates in a manner that involves a significant portion of the extra power being exhausted into a heat. Meanwhile, when a buck converter is implemented as an integrated circuit, the buck converter is commonly used because at least 95% of the power supplied to it can be converted.
The buck converter coupled with a LED (Light Emitting Diode) may include a switch controlling a current that flows to the LED, a sensing circuit that measures the load current, for example for a load series-coupled to the LED and the inductor, and a control circuit controlling the switch based on the measured load current to control constantly maintaining a load average current.
Various technologies relate to an average inductor current mode switching converters and relate to a control circuit and a method for regulating an average inductor current in switching converter. These technologies disclose aspects of a control circuit controlling a load current on the power supply.
FIG. 1 illustrates a waveform diagram of a load current controlled by a control circuit.
Referring to FIG. 1, an x-axis and a y-axis respectively represent a time and a current value. Thus, FIG. 1 illustrates how the load current changes over time.
The control circuit of FIG. 1 senses a current that flows to a load through a sensing circuit and stores a time when a sensed current reaches a predefined reference current value REF. For example, the control circuit stores a reach time T1, where the reach time T1 indicates a time from when a switch controlling a current is turned on to a time when the sensed current reaches the predefined reference current value REF.
The control circuit counts the reach time T1 stored at a time when the sensed current reaches the predefined reference current REF and turns off a switch at an elapsed time T2 corresponding to the reach time T1. The average current of the load current is maintained at the predefined reference current REF.
In such a control circuit, the load current is assumed to constantly increase. However, when the load current does not constantly change, there is an issue that it is difficult to control the average current so that the average current is substantially the same as the reference current.
Also, such a control circuit includes an intermediate operational circuit for determining the reach time when the sensed current reaches the reference current and storing the determined reach time. Therefore, such a control circuit presents issues that a delay time for a current control occurs and it is difficult to control the average current according to a change of the input power and the load.